Plasticity-tunable neodymium-iron-boron magnet with homogeneous functional motif architecture and preparation method

Abstract

This invention discloses a homogeneous functional unit-structured, plastically tunable NdFeB magnet and its preparation method, belonging to the field of rare earth permanent magnet materials technology. Addressing the core problems of poor plasticity (elongation typically <0.5%) and brittle fracture in traditional NdFeB magnets, the magnet designed in this invention comprises, by mass percentage: 28-32% Nd, 66-70% Fe, 1-3% B, 0.1-5% rare earth functional units (one or more of Dy, Tb, and Pr), and 0.1-5% plasticity-tuning functional units. By constructing a nanoscale homogeneous structure (average grain size 500-5000 nm), this magnet not only maintains excellent magnetic properties (coercivity ≥1000 kA / m, remanence ≥1.2 T, maximum energy product ≥300 kJ / m³) at 20℃, but also significantly improves elongation. The preparation process involves cleaning and removing impurities from raw materials, powdering and modification, external field-induced pre-pressing, pre-pressing annealing and low-temperature sintering, aging heat treatment and coating. It precisely controls the uniform distribution of the plastic phase at the grain boundaries, achieving synergistic optimization of magnetic properties and plasticity, and breaking through the technical bottleneck of "high magnetic properties inevitably lead to brittleness" in traditional NdFeB.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials technology, specifically relating to a plastically tunable NdFeB magnet with a homogeneous functional unit order structure and its preparation method, which is particularly suitable for precision electronics, new energy vehicles and high-end equipment manufacturing and other fields that require high magnetic properties and good plastic deformation capabilities. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are widely used in high-tech fields such as new energy vehicle drive motors, wind power generation, and nuclear magnetic resonance imaging (MRI) equipment due to their excellent magnetic properties. These magnets, with their high remanence, high coercivity, and high energy product, have become core functional materials in modern industry and electronic equipment. However, traditional NdFeB magnets are essentially intermetallic compounds, and the covalent and ionic bonds in their crystal structure result in significant intrinsic brittleness, making them highly susceptible to cleavage fracture under complex stresses such as bending and torsion. This defect not only limits the application of magnets in precision mechanical components but also poses a serious challenge to the reliability of their processing.

[0003] Currently, academia and industry have conducted extensive research to improve the plasticity of NdFeB magnets. While adding alloying elements such as Co, Ga, and Nb to regulate the crystal structure can improve toughness to some extent, it also reduces magnetocrystalline anisotropy, thereby weakening remanence and energy product. Optimizing the microstructure using processes such as hot deformation and magnetic field orientation can refine the grains, but the disordered distribution of grain boundary phases remains, and excessively high processing temperatures can cause abnormal grain growth, further deteriorating overall performance. More importantly, in traditional powder metallurgy manufacturing processes, due to the inhomogeneity of the sintering process, a significant gradient structure exists within the magnet, with substantial differences in mechanical properties between coarse-grained and fine-grained regions. This structural defect further exacerbates the risk of magnet failure.

[0004] Therefore, overcoming existing technological bottlenecks requires innovative material design concepts. There is an urgent need to develop a novel neodymium iron boron magnet based on homogeneous functional unit order, which, through precise control of atomic-scale phase interfaces and nanoscale microstructure, can achieve a synergistic improvement in plasticity while maintaining high magnetic performance. Simultaneously, the supporting fabrication process must consider both the microstructure control and macroscopic performance optimization of the magnet, which will open new avenues for the engineering application of high-performance magnetic materials. Summary of the Invention

[0005] To address technical problems such as reduced magnetocrystalline anisotropy, disordered grain boundary phase distribution, and abnormal grain growth, this invention provides a plastically tunable NdFeB magnet with a homogeneous functional unit ordered structure and its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a plastically tunable neodymium iron boron magnet with a homogeneous functional unit sequence structure.

[0008] A homogeneous functional unit structure of a plastically tunable NdFeB magnet, comprising soft magnetic phase functional units, hard magnetic phase functional units, and plastic phase functional units, and composed of the following materials in mass percentage: 28-32% Nd, 66-70% Fe, 1-3% B, 0.1-5% rare earth functional units, and 0.1-5% plasticity regulating functional units; wherein the rare earth functional units are one or more of Dy, Tb, and Pr; and the plasticity regulating functional units are one or more of Al, Nb, Ti, Zr, Ce, La, Cu, or Ga.

[0009] Furthermore, the neodymium iron boron magnet has a nanoscale homogeneous structure with an average grain size of 500~5000 nm and a size distribution standard deviation ≤10%; at 20℃, it has a coercivity Hc≥1000kA / m, remanence Br≥1.2T, and maximum energy product BHmax≥300kJ / m. 3 Elongation ≥1%.

[0010] Furthermore, the volume fraction of the soft magnetic phase functional unit is [I1~I2]%, and the volume fraction of the hard magnetic phase functional unit is [J1~J2]%, and [I1~I2]+[J1~J2]=100%.

[0011] A second aspect of the present invention provides a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit order, comprising the following steps:

[0012] Step 1, Raw material cleaning and impurity removal: Select raw materials according to mass percentage, including 28~32% Nd, 66~70% Fe, 1~3% B, 0.1~5% rare earth functional units and 0.1~5% plasticity regulation functional units, and then clean and remove impurities;

[0013] Step 2, Powder Preparation and Modification: Using an air jet mill or mechanical alloying process, Nd, Fe, B, rare earth functional units, and plasticity control functional units are uniformly dispersed to obtain alloy powder with an average particle size of 300–3000 nm and a particle size distribution standard deviation ≤10%. The alloy powder is then mixed and stirred with a silane coupling agent functional unit solution. Surface modification functional units further improve the dispersibility of the alloy powder, causing some Fe elements to form soft magnetic phase micronuclei α-Fe and Fe3B, while Nd, B, and some Fe elements form a hard magnetic phase precursor Nd2Fe. 14B. Plasticity regulation functional units form plastic phase functional unit precursors through diffusion and reaction, completing the synergistic dispersion and particle size matching of the three phases to obtain modified powder; (the particle size distribution of the powder is monitored online by a laser particle size analyzer, and the process parameters are adjusted in real time to ensure that the standard deviation of the particle size distribution of each functional unit is ≤10%, thereby achieving uniform control of the grain size.)

[0014] Step 3, External Field Induced Pre-pressing: The modified powder of the homogeneous functional unit ordered structure is loaded into the mold for pre-pressing. At the same time, the soft magnetic phase micronuclei are oriented and aligned by the external field induction of the magnetic field or electric field. After the soft magnetic phase micronuclei are oriented and aligned, the hard magnetic phase prototype is simultaneously formed and distributed in an orderly manner. The plastic phase functional unit precursor is dispersed and rheologically arranged in the grain boundary region along with the arrangement of the soft magnetic phase micronuclei and the hard magnetic phase prototype, forming a molded green body of the homogeneous functional unit ordered structure; laying the foundation for the subsequent construction of the ordered structure system;

[0015] Step 4, Pre-press annealing and low-temperature sintering: The formed green body undergoes pre-press annealing pretreatment. Through functional unit diffusion regulation, the rheologically arranged plasticity-controlled functional unit precursors form nano-tough plastic phase functional units in the grain boundary region. Then, low-temperature sintering forms an amorphous interface ordered layer, allowing soft magnetic phase micronuclei to aggregate and grow in specific regions, and hard magnetic phase nascent grains to grow, forming both soft and hard magnetic phase functional units, yielding Nd₂Fe. 14 B-type plasticity-regulated composite functional unit;

[0016] Step 5, Aging heat treatment and coating: By applying Nd2Fe... 14 B. Plasticity-controlled composite functional units undergo aging heat treatment to precipitate and regulate dislocation order structure, adjust the distribution of soft magnetic phase functional units, optimize the structure of hard magnetic phase functional units, and apply a 1-5 μm thick Zn-Ni or Al-Ti composite functional unit coating by physical vapor deposition. The Zn-Ni or Al-Ti composite functional unit coating enhances corrosion resistance and plastic deformation coordination, resulting in a plastically tunable NdFeB magnet with a homogeneous functional unit order structure.

[0017] The soft magnetic phase functional units and hard magnetic phase functional units form a three-dimensional ordered gradient structure system through exchange coupling. The plastic phase functional units are uniformly distributed at the grain boundaries of the soft magnetic phase and the hard magnetic phase, and work together with the soft magnetic phase and the hard magnetic phase to construct a "magnetic-plastic" dual-function synergistic structure. The plastic phase functional units can alleviate grain boundary stress concentration and enhance the overall plastic deformation capability of the magnet.

[0018] Furthermore, the soft magnetic phase functional unit is one or more of α-Fe, Fe3B, Fe-Dy solid solution, and Fe-Tb solid solution; the hard magnetic phase functional unit is Nd2Fe. 14 B, Pr2Fe 14 B、(Ce,Nd)2Fe 14One or more of B; the plastic phase functional unit is an Al-rich region, AlFe2 intermetallic compound, TiB2 nanoparticles, TiC microparticles, ZrB2 nanoparticles, ZrC microparticles, CeFe2 Laves phase, (Ce,Nd)2Fe 14 B main phase, LaFe2 Laves phase, Nd-Cu composite phase, Cu enrichment region, Nd6Fe 13 Ga nanophase, Ga-RE micron composite phase, NbB2 nanoparticles, Nb-RE micron composite phase; TiB2+AlFe2 composite nanophase, TiC+Al enriched micron region, ZrB2 framework + Dy2Fe 14 B-shell, Nd6Fe 13 Ga nanophase + (Ce,Nd)2Fe 14 B main phase, Ga-Ce micron composite phase, NbB2 nanoparticles + Cu coated micron layer, TiB2 / ZrB2 eutectic nanophase, TiC / ZrC micron eutectic phase, AlFe2 nanoparticles + Nd6Fe 13 One or more Ga microphases.

[0019] Furthermore, the silane coupling agent functional unit solution is one of the following: γ-aminopropyltriethoxysilane (KH550) solution, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792) solution, γ-glycidoxypropyltrimethoxysilane (KH560) solution, γ-glycidoxypropyltriethoxysilane (A-187) solution, γ-methacryloyloxypropyltrimethoxysilane (KH570) solution, vinyltriethoxysilane (A-151) solution, γ-mercaptopropyltrimethoxysilane (KH580) solution, or γ-mercaptopropyltriethoxysilane (A-189) solution;

[0020] The surface-modifying functional unit is one of the following: γ-aminopropyltriethoxysilane (KH550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), γ-glycidyl etheroxypropyltrimethoxysilane (KH560), γ-glycidyl etheroxypropyltriethoxysilane (A-187), γ-methacryloyloxypropyltrimethoxysilane (KH570), vinyltriethoxysilane (A-151), γ-mercaptopropyltrimethoxysilane (KH580), γ-mercaptopropyltriethoxysilane (A-189), isopropyltris(dioctylpyrophosphoyloxy)titanate (TTOP-12), tetraisopropyldi(dioctylphosphite)titanate (TIPT), distearate isopropyl aluminate (DL-411), stearic acid, or oleic acid.

[0021] Furthermore, the volume fraction of the soft magnetic phase functional unit is 1-30%; the volume fraction of the hard magnetic phase functional unit is 70-99%; the volume fraction of the plastic phase functional unit is 0.1-5%; and the sum of the volume fractions of the plastic phase functional unit, the soft magnetic phase functional unit, and the hard magnetic phase functional unit is 100%.

[0022] The aforementioned volume fractions of each functional phase are designed to balance magnetic and mechanical properties. The hard magnetic phase, comprising 70-99%, ensures the material possesses excellent hard magnetic characteristics such as high remanence and high coercivity, meeting the core requirements of permanent magnet applications. The soft magnetic phase, comprising 1-30%, optimizes the magnetic energy product through magnetic exchange coupling, enhancing overall magnetic performance. Secondly, the 0.1-5% ductile phase effectively improves material brittleness, enhances toughness and processing performance, and solves the problems of easy fracture and difficult processing of hard magnetic materials, facilitating subsequent molding and application. Furthermore, the sum of the volume fractions of all three phases is 100%, avoiding component waste or performance redundancy, ensuring stable material composition and synergistic functions, and adapting to the high-performance permanent magnet material requirements of various fields such as motors and sensors.

[0023] Furthermore, the average particle size of the soft magnetic phase functional unit is 100~1000nm, and it is uniformly dispersed among the hard magnetic phase functional units; the average grain size of the hard magnetic phase functional unit is consistent with the average grain size of the magnet, which is 500~5000nm; the average size of the plastic phase functional unit is 5~500nm, and it forms a gradient distribution with the distribution of the soft magnetic phase and the hard magnetic phase.

[0024] The aforementioned particle size and distribution design offers significant advantages. The soft magnetic phase, with uniformly dispersed particles of 100–1000 nm, maximizes the contact area with the hard magnetic phase, enhancing exchange coupling and improving magnetic stability. The hard magnetic phase, with grain sizes of 500–5000 nm, matches the overall magnet size, ensuring compliance with primary magnetic properties and avoiding performance losses due to grain mismatch. The ductile phase, with a gradient distribution of 5–500 nm, adapts to and fills the magnetic phase interface, enhancing interfacial bonding without interfering with the magnetic structure, alleviating stress concentration, and improving the overall mechanical toughness and fatigue resistance of the material. The synergistic size distribution of these three phases balances magnetic domain control and structural strengthening, allowing the material to possess both strong magnetic properties and good processability and reliability.

[0025] Furthermore, the cleaning and impurity removal in step 1 specifically involves: ultrasonic cleaning at a frequency of 20-40 kHz for 10-30 minutes, followed by cleaning under a vacuum of 10... -2 Impurities were removed by vacuum drying at 80~100℃.

[0026] The above-mentioned cleaning and impurity removal solution offers significant advantages. Ultrasonic cleaning at 20-40kHz for 10-30 minutes effectively removes oil, dust, and other impurities from the raw material surface using high-frequency vibration, without damaging the particle structure of the raw material, thus balancing cleaning power and protection. Subsequent drying at 10⁻²Pa high vacuum and 80-100℃ quickly removes residual moisture after cleaning, while preventing oxygen and impurities in the air from reacting with the raw material during heating, ensuring its purity. The entire process, combining physical impurity removal with vacuum drying, effectively reduces the interference of impurities on subsequent magnet preparation and performance, laying the foundation for the excellent magnetic properties and structural stability of the final product.

[0027] Furthermore, the air jet milling or mechanical alloying process in step 2 specifically involves controlling the air jet mill inlet pressure to be 0.6~0.8MPa and the temperature to be 20~30℃, or the mechanical alloying rotation speed to be 200~500r / min and the ball-to-material ratio to be 10~20:1.

[0028] The above-mentioned process parameter settings offer significant advantages. The air jet mill controls the inlet air pressure at 0.6~0.8MPa and the temperature at 20~30℃, ensuring sufficient airflow energy for efficient grinding of the raw material to the target particle size, while avoiding excessive pressure leading to over-crushing of particles and excessive temperature causing oxidation of the raw material, thus ensuring uniform powder particle size and high purity. Mechanical alloying uses a rotation speed of 200~500r / min and a ball-to-material ratio of 10~20:1. Appropriate impact and grinding force achieve thorough alloying of the raw material. The reasonable combination of rotation speed and ball-to-material ratio prevents incomplete alloying due to insufficient energy and powder adhesion or contamination due to excessive energy, providing high-quality powder raw materials for subsequent magnet manufacturing and ensuring stable performance of the final product.

[0029] Furthermore, the mixing and stirring treatment in step 2 specifically involves mixing the alloy powder with the silane coupling agent functional element solution at a mass ratio of 1:0.01~0.05, and treating it at 30~50℃ and a stirring rate of 200~400 r / min for 30~60 min.

[0030] The above-mentioned mixing and stirring parameters offer significant advantages. A mass ratio of 1:0.01~0.05 for the alloy powder and silane coupling agent solution ensures the coupling agent fully coats the powder surface, improving its dispersibility and interfacial bonding, while avoiding waste or negative impacts on magnetic properties due to excessive coupling agent. A temperature of 30~50℃ and a stirring speed of 200~400 r / min are well-matched; the temperature promotes efficient interaction between the coupling agent and powder, the speed ensures uniform mixing without damaging the powder structure, and the processing time of 30~60 min ensures a complete reaction. The synergistic effect of these parameters enhances the processing performance of the alloy powder and subsequent molding effects, guaranteeing the excellent structural stability and magnetic properties of the magnet.

[0031] Furthermore, in step 3, the modified powder is loaded into the mold for pre-pressing, and the external field induction by magnetic field or electric field is specifically: the pressure is maintained at 10~15MPa and 15~25℃ for 5~10min; the magnetic field strength induced by the external field is 0.5~1T, and the electric field strength induced by the external field is 1~10kV / m.

[0032] The aforementioned pre-compression and external field induction parameter design offers significant advantages. A pressure of 10-15 MPa and a holding time of 5-10 minutes at 15-25°C allow the modified powder to initially form a structurally stable green body, preventing powder agglomeration due to excessive pressure or loosening of the green body due to insufficient pressure. The ambient temperature also prevents temperature from affecting the magnetic properties of the powder. A magnetic field of 0.5-1 T or an electric field of 1-10 kV / m effectively controls the orientation of magnetic domains in the powder, improving the anisotropy and magnetic properties of the magnet. The moderate external field strength avoids energy waste or structural damage caused by excessively strong external fields. The synergistic effect of these parameters lays a solid foundation for subsequent sintering and ensures that the final magnet possesses both a stable structure and excellent magnetic properties.

[0033] Furthermore, in step 4, the pre-compression pressure of the pre-compression annealing pretreatment is 5~10 MPa, the annealing temperature is 600~750℃, and the annealing time is 0.5~1 h; in step 4, the low-temperature sintering is carried out in a vacuum sintering furnace, where the temperature is raised to 1020~1080℃ at a heating rate of 3~5℃ / min and held for 1.5~2.5 h, and the vacuum degree of the vacuum sintering furnace is 10. -3 ~10 -4 Pa.

[0034] The aforementioned pretreatment and sintering parameter design offers significant advantages. Pre-compression of 5-10 MPa combined with annealing at 600-750℃ for 0.5-1 h maintains the green body morphology under appropriate pressure, eliminates internal stress and removes residual impurities at medium temperatures, and prevents premature grain growth due to high temperatures, laying the foundation for subsequent sintering. Low-temperature sintering, with a slow heating rate of 3-5℃ / min to 1020-1080℃, allows for uniform grain growth and reduces structural defects; 1.5-2.5 h of holding time and 10⁻³-10⁻ 4 High vacuum (Pa) ensures thorough sintering and prevents raw material oxidation. The entire process balances structural densification and performance stability, helping the magnet form an excellent microstructure and guaranteeing its hard magnetic properties and mechanical performance.

[0035] Furthermore, the aging heat treatment in step 5 is applied to Nd2Fe 14 B plasticity-regulating composite functional unit is heated to 800~950℃, held for 1~10h and then cooled with the furnace.

[0036] The aforementioned aging heat treatment parameters offer significant advantages. A heating temperature of 800–950℃ activates atomic diffusion within the magnet, promoting grain refinement and uniform distribution of the hard magnetic phase, optimizing the magnetic domain structure, and thus enhancing the magnet's coercivity and magnetic stability. This temperature range also prevents excessively high temperatures from causing abnormal grain growth or magnetic phase decomposition. A holding time of 1–10 hours provides ample time for sufficient atomic diffusion and internal stress release, ensuring proper microstructure adjustment. Furnace cooling slows the cooling rate, preventing the formation of new internal stresses or structural defects due to excessive temperature differences. This entire process further improves the magnet's microstructure, enhances magnetic durability and mechanical reliability, and ensures stable performance during long-term use.

[0037] Furthermore, by controlling the angle between the direction of the magnetic field or electric field and the expected direction of plastic deformation to be ≤15°, a dominant path for plastic deformation can be constructed.

[0038] The aforementioned control of the magnetic / electric field direction with an angle ≤15° between the direction and the expected direction of plastic deformation offers significant advantages. Firstly, this small angle ensures that the orientation of the magnetic / electric domains induced by the external field closely matches the deformation direction, constructing a clear advantageous path for plastic deformation, reducing internal stress concentration during deformation, and lowering the risk of magnet cracking. Secondly, it guides the distribution of functional units in the plastic phase along the advantageous path, strengthening interfacial bonding and improving the material's toughness and ductility in the expected deformation direction, avoiding performance losses caused by deformation in unintended directions. Thirdly, this directional control ensures that the magnet retains excellent magnetic properties after deformation, balancing processability and performance, making it suitable for applications such as motors and sensors that require precise magnet shape and performance.

[0039] Furthermore, by adjusting the content of plasticity control functional units (0.1~1%) and annealing temperature (600~750℃), the thickness of the amorphous interface ordered layer (5~20nm) can be controlled, thereby achieving adjustable ordering of magnet elongation within the range of 1~12%.

[0040] The aforementioned control scheme offers significant advantages. By synergistically adjusting the content of 0.1–1% of the plasticity control functional building blocks and the annealing temperature of 600–750℃, the thickness of the 5–20 nm amorphous interface ordered layer can be precisely controlled, providing crucial support for adjusting the magnet's elongation. The amorphous interface layer can alleviate phase interface stress, and its thickness change is directly related to the material's toughness. Combined with adjustments to the plasticity building block content, an ordered elongation of 1–12% can be achieved. This satisfies the magnet rigidity requirements of low elongation scenarios while also adapting to the processability requirements of high elongation scenarios. Furthermore, the adjustable range of annealing temperature and plasticity building block content avoids excessive adjustment that could lead to a decrease in magnetic properties, balancing mechanical property adjustability with magnetic property stability.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] This invention pioneers a nanoscale homogeneous functional unit ordered structure system, through Nd2Fe 14 The B hard magnetic phase, α-Fe / Fe3B soft magnetic phase, and plasticity-regulating phases (such as AlFe2, TiB2, etc.) are orderly distributed in three-dimensional space, forming a soft magnetic-hard magnetic phase that enhances the magnetic energy product through exchange coupling. The grain boundary plastic phase alleviates the hierarchical structure of stress concentration. At the same time, a laser particle size analyzer is used to monitor the powder particle size distribution in real time (standard deviation ≤50nm) to ensure that the functional units are uniformly dispersed, solving the performance fluctuation problem caused by component segregation in traditional magnets. The innovative introduction of a multi-selection mechanism of eight plasticity-regulating elements such as Al, Nb, Ti, and Zr allows for flexible customization of component combinations according to application scenarios. For example, the Ti / Zr combination improves fatigue resistance, the Cu / Ga combination enhances plastic deformation coordination, and Ce / La partially replaces Nd to reduce dependence on heavy rare earth elements. This achieves a balanced optimization of "magnetism-plasticity-cost", which is in stark contrast to the single-phase or simple composite structure of traditional NdFeB magnets, and achieves synergistic enhancement of magnetic properties and plasticity.

[0043] This invention successfully addresses the brittleness problem of NdFeB magnets by establishing a cross-scale interface control system from nanoscale grain boundaries to macroscopic coatings. At the microscale, pre-pressing annealing and low-temperature sintering processes induce the formation of a 5-20 nm thick amorphous Nd-Ti-Zr-O composite layer at the grain boundaries using plasticity-regulating elements. This composite layer combines magnetoresistance barrier function (maintaining coercivity Hc ≥ 1000 kA / m) with stress concentration mitigation. Unlike traditional magnets with a single grain boundary phase, this amorphous interface layer allows for precise thickness control by adjusting the Ti / Zr content and annealing temperature, enabling continuous adjustment of elongation within the range of 1-12%, far exceeding the 0.3% limit of existing technologies. At the macroscale, innovative physical vapor deposition (PVD) is used to coat Zn-Ni or Al-Ti composite coatings. The use of metallic bonding functional units enhances the adhesion between the coating and the substrate, enabling a neutral salt spray corrosion resistance time exceeding 1000 hours, effectively resolving the contradiction of "high plasticity necessarily weak corrosion resistance." This dual-interface design of "nano-grain boundary reinforcement + macro-coating protection" achieves simultaneous improvement in the mechanical properties and environmental stability of NdFeB magnets.

[0044] This invention achieves precise control over structure and performance by developing an integrated external field-guided directional control and low-temperature sintering process. During molding, the external field induces the directional alignment of soft magnetic phases, creating a favorable path for plastic deformation and significantly reducing internal stress defects. In the sintering stage, a low-temperature, high-vacuum process is employed to suppress excessive grain growth and promote the uniform diffusion of plasticity-regulating elements to form ordered phases. Furthermore, precise control of process parameters throughout the entire process, coupled with multi-step thermal processes, significantly improves the magnet yield.

[0045] This invention breaks with traditional understanding, achieving a breakthrough in the synergistic combination of high magnetic properties and high plasticity in NdFeB magnets. Through the gradient distribution design of plasticity control elements and an innovative "dislocation sequence control" mechanism, the magnet achieves both high-end magnetic properties and an elongation of 1-12% without sacrificing the magnetic energy product. Furthermore, based on the "one material, multiple functions" concept, by changing the type and content of plasticity control elements, the magnet's performance can be customized to meet the needs of various scenarios such as new energy vehicle motors and wind power equipment, significantly expanding the application boundaries of NdFeB magnets. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a magnet sample with a structure in which the soft magnetic phase, hard magnetic phase, and plastic phase are arranged in a gradient according to the present invention.

[0048] Figure 2 This is a SEM scan of the structure of the present invention, which features a gradient arrangement of soft magnetic phase, hard magnetic phase, and plastic phase.

[0049] Figure 3 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0050] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.

[0051] Example 1

[0052] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0053] Step 1: Select Nd 28%, Fe 70%, B 1%, rare earth functional unit Dy 0.1%, and plasticity regulating unit Ti 0.1% by mass percentage; use 20kHz ultrasonic cleaning for 30min, followed by vacuum drying at 80℃ and 10⁻²Pa to remove oil and oxide layer from the surface of the raw materials.

[0054] Step 2: Powder was prepared using an air jet mill, with the inlet pressure controlled at 0.6 MPa and the internal temperature at 20°C, to obtain alloy powder with an average particle size of 1500 nm and a particle size distribution standard deviation of 42 nm. The alloy powder was mixed with a γ-aminopropyltriethoxysilane (KH550) solution at a mass ratio of 1:0.01 and treated at 30°C and a stirring rate of 200 r / min for 60 min. The powder dispersibility and surface activity were improved by using a silane coupling agent.

[0055] Step 3: Load the modified powder into the mold and hold it under pressure of 10MPa and 15℃ for 10min. At the same time, apply a 0.5T magnetic field (the magnetic field direction is 15° away from the expected direction of plastic deformation) to induce the soft magnetic phase to align and form a molded blank with a homogeneous functional unit structure.

[0056] Step 4: Pre-press annealing is performed on the formed blank, with the pre-press pressure controlled at 5 MPa, the annealing temperature at 600℃, and the holding time at 1 h, to promote the diffusion of Ti elements at the grain boundaries; then low-temperature sintering is performed, with the temperature increased to 1020℃ at a heating rate of 3℃ / min, and held at 10⁻³Pa for 2.5 h under vacuum conditions, so that Ti and O combine to form an amorphous Nd-Ti-O interface ordered layer.

[0057] Step 5: The sintered magnet is aged at 800℃ for 2 hours and then cooled in the furnace to precipitate trace amounts of Ti-rich intermetallic compounds to regulate the dislocation order structure; a 1μm thick Zn-Ni coating is applied using physical vapor deposition (PVD) technology to enhance corrosion resistance.

[0058] Final performance: average grain size of magnet 800nm ​​(size distribution standard deviation 8%), coercivity Hc=1250kA / m, remanence Br=1.25T, maximum energy product (BHmax)=300kJ / m³, elongation=1.2%, and corrosion resistance time of 850h in neutral salt spray test at 20℃.

[0059] Example 2

[0060] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0061] Step 1: Select Nd 30%, Fe 68%, B 2%, rare earth functional unit Tb 2.5%, and plasticity regulating unit Zr 0.5% by mass percentage; clean with 30kHz ultrasonic for 20 minutes, and vacuum dry at 90℃ and 10⁻²Pa.

[0062] Step 2: Using air jet milling, the inlet pressure was controlled at 0.7 MPa and the temperature at 25 ℃ to obtain alloy powder with an average particle size of 2000 nm and a particle size distribution standard deviation of 38 nm. The powder was mixed with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792) solution at a mass ratio of 1:0.03 and treated at 40 ℃ and a stirring rate of 300 r / min for 45 min. Simultaneously, 0.1% stearic acid was added as a surface modification aid.

[0063] Step 3: Hold the pressure at 12MPa and 20℃ for 8 minutes, then apply a 0.7T magnetic field (with the magnetic field at an angle of 10° to the deformation direction) to induce molding and form a preform.

[0064] Step 4: Pre-compression pressure 7MPa, anneal at 650℃ for 0.8h to promote Zr element diffusion; heat to 1050℃ at 4℃ / min, under vacuum of 10⁻ 4 Sintering at Pa for 2 hours under these conditions forms an amorphous Nd-Zr-O interface layer.

[0065] Step 5: Aging treatment at 900℃ for 1.5h, followed by furnace cooling; 3μm thick Al-Ti composite coating is applied using PVD to enhance the adhesion between the coating and the substrate through metallic bonds.

[0066] Final performance: average grain size 1200nm (standard deviation 7%), Hc=1500kA / m, Br=1.25T, (BH)max=320kJ / m³, elongation increased to 8%, and corrosion resistance time in neutral salt spray test exceeds 1200h.

[0067] Example 3

[0068] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0069] Step 1: Select Nd 32%, Fe 66%, B 3%, rare earth functional unit Pr 5%, and plasticity control unit Ti 0.8% by mass percentage; clean with 40kHz ultrasonic for 10 min, and vacuum dry at 100℃ and 10⁻²Pa.

[0070] Step 2: Powder is prepared by mechanical alloying process, with a rotation speed of 300 r / min and a ball-to-powder ratio of 15:1 (the grinding balls are made of WC material), to obtain alloy powder with an average particle size of 5000 nm and a particle size distribution standard deviation of 45 nm; the powder is mixed with γ-glycidyl etheroxypropyltrimethoxysilane (KH560) solution at a mass ratio of 1:0.05 and treated at 50 °C and a stirring rate of 400 r / min for 30 min.

[0071] Step 3: Hold the pressure at 15MPa and 25℃ for 5 minutes, apply a 5kV / m electric field (the electric field is at an angle of 5° to the deformation direction) to induce molding, and use the electric field force to promote the directional arrangement of functional units.

[0072] Step 4: Pre-compression pressure 10MPa, annealing at 700℃ for 0.5h; heating to 1080℃ at 5℃ / min, vacuum degree 10⁻ 4 Sintering at Pa for 1.5 h under these conditions resulted in the formation of TiB2 nanoparticle-enhanced grain boundary order.

[0073] Step 5: Aging treatment at 850℃ for 1 hour, followed by furnace cooling; PVD coating of a 5μm thick Zn-Ni / Al-Ti composite coating (3μm Zn-Ni layer + 2μm Al-Ti layer).

[0074] Final performance: average grain size 1500 nm (standard deviation 9%), Hc=1400 kA / m, Br=1.3 T, (BH)max=350 kJ / m³, elongation up to 10%, salt spray resistance time over 1500h.

[0075] Example 4

[0076] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0077] Step 1: Select Nd 29%, Fe 69%, B 1.5%, rare earth functional unit (Dy 1% + Tb 1%), and plasticity control unit Ti 0.3% by mass percentage; clean with 35kHz ultrasonic for 15min, and vacuum dry at 95℃ and 10⁻²Pa.

[0078] Step 2: Air jet milling was performed, with the inlet pressure controlled at 0.8 MPa and the temperature at 30 °C, to obtain an alloy powder with an average particle size of 3500 nm and a particle size distribution standard deviation of 40 nm; the powder was then mixed with a γ-methacryloyloxypropyltrimethoxysilane (KH570) solution at a ratio of 1:0.03 and treated at 45 °C and 350 r / min for 40 min.

[0079] Step 3: Hold pressure at 11MPa and 18℃ for 7 minutes, then apply a 0.9T magnetic field (angle 8°) to induce molding.

[0080] Step 4: Pre-press 6MPa, anneal at 750℃ for 0.6h; sinter at 1030℃ with a heating rate of 3.5℃ / min and a vacuum of 10⁻³Pa for 2.3h to form a Dy-Tb-Ti composite oxide interface layer.

[0081] Step 5: Aging at 880℃ for 1.8h, then coating with a 2μm Zn-Ni coating.

[0082] Final performance: average grain size 1700nm (standard deviation 8%), Hc=1250kA / m, Br=1.22T, (BH)max=310kJ / m³, elongation=7%, salt spray resistance time 1000h.

[0083] Example 5

[0084] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0085] Step 1: Select Nd 31%, Fe 67%, B 2.5%, rare earth functional unit Pr 3%, and plasticity regulating unit Zr 0.7% by mass percentage; clean with 30kHz ultrasonic for 18min, and vacuum dry at 92℃ and 10⁻²Pa.

[0086] Step 2: Mechanical alloying powder preparation, with a rotation speed of 500 r / min and a ball-to-powder ratio of 20:1, to obtain alloy powder with an average particle size of 4500 nm and a particle size distribution standard deviation of 48 nm; mix with vinyltriethoxysilane (A-151) solution at a ratio of 1:0.04, and treat at 48℃ and 380 r / min for 35 min.

[0087] Step 3: Hold at 14MPa pressure and 22℃ for 6 minutes, then apply an electric field of 10kV / m (angle 12°) to induce molding.

[0088] Step 4: Pre-pressurize at 8 MPa, anneal at 680℃ for 0.7 h; sinter at 1060℃ with a heating rate of 4℃ / min and a vacuum of 10⁻³Pa for 2.2 h to form ZrB2 nanophase-reinforced grain boundaries.

[0089] Step 5: Aging at 820℃ for 1.6 hours, then coating with a 4μm Al-Ti coating.

[0090] Final performance: average grain size 2300nm (standard deviation 9%), Hc=1350kA / m, Br=1.28T, (BH)max=330kJ / m³, elongation=9%, salt spray resistance time 1300h.

[0091] Example 6

[0092] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0093] Step 1: Select Nd 30%, Fe 67.5%, B 2%, rare earth functional unit (Dy 2% + Pr 1%), and plasticity control unit (Ti 0.5% + Zr 0.5%) by mass percentage; clean with 35kHz ultrasonic for 20 min, and vacuum dry at 95℃ and 10⁻²Pa.

[0094] Step 2: Using a combined process of "air jet milling coarse powder + mechanical alloying fine powder", coarse powder of 3000nm is first obtained by air jet milling at 0.7MPa, and then mechanical alloying is performed at 400r / min and ball-to-powder ratio of 18:1 for 1h to obtain ultrafine alloy powder with an average particle size of 500nm and a particle size distribution standard deviation of 30nm; it is then mixed with γ-mercaptopropyltrimethoxysilane (KH580) solution at 1:0.04 and treated at 45℃ and 350r / min for 35min.

[0095] Step 3: Hold at 13MPa pressure and 23℃ for 9 minutes, then apply a 1T magnetic field (angle 3°) to induce molding and maximize the orientation of the soft magnetic phase.

[0096] Step 4: Pre-compression pressure 9MPa, annealing at 720℃ for 0.9h; heating to 1070℃ at 4.5℃ / min, vacuum degree 10⁻ 4 Sintering at Pa for 2 hours under Pa conditions forms an amorphous interface layer of Ti-Zr composite oxide.

[0097] Step 5: Aging at 860℃ for 1.7h, then coating with a 3.5μm Zn-Ni / Al-Ti composite coating (Zn-Ni 2μm + Al-Ti 1.5μm).

[0098] Final performance: average grain size 300nm (standard deviation 6%), Hc=1380kA / m, Br=1.27T, (BH)max=340kJ / m³, elongation up to 12% (the highest value in the Chuangben series formula), salt spray resistance time over 1600h.

[0099] Comparative Example 1

[0100] Step 1: Select Nd 30%, Fe 68%, B 2%, and rare earth functional unit Dy 2.5% by mass percentage, without adding plasticity control unit; use 30kHz ultrasonic cleaning for 20 minutes, and vacuum dry at 90℃.

[0101] Step 2: Using conventional airflow milling with an inlet pressure of 0.5 MPa and a temperature of 35°C, an alloy powder with an average particle size of 2000 nm and a particle size distribution standard deviation of 26% was obtained without silane coupling agent treatment.

[0102] Step 3: Cold pressing is performed under 10MPa pressure without external field induction, resulting in disordered distribution of functional units inside the blank.

[0103] Step 4: Using the traditional high-temperature sintering process, hold at 1100℃ for 3 hours with a vacuum degree of 10⁻²Pa.

[0104] Step 5: No aging treatment or coating was applied.

[0105] Final performance: average grain size 1200nm (standard deviation 22%), Hc=850kA / m, Br=0.8T, (BH)max=280kJ / m³, elongation only 0.002% (exhibiting typical brittle fracture characteristics), salt spray resistance time less than 200h.

[0106] Example 7

[0107] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0108] Step 1: Select Nd 29.5%, Fe 69%, B 1.2%, rare earth functional element Pr 1.8%, and plasticity regulating element Al 0.5% by mass percentage; clean with 25kHz ultrasonic for 25min, and vacuum dry at 85℃ and 10⁻²Pa.

[0109] Step 2: Air jet milling was performed at an inlet pressure of 0.65 MPa and a temperature of 22 °C to obtain an alloy powder with an average particle size of 2500 nm and a particle size distribution standard deviation of 43 nm. The powder was then mixed with a γ-aminopropyltriethoxysilane (KH550) solution at a ratio of 1:0.02 and treated at 35 °C and 250 r / min for 50 min. 0.05% distearyloxyisopropyl aluminate was added for auxiliary modification.

[0110] Step 3: Hold at 12MPa pressure and 20℃ for 8 minutes, then apply a 0.6T magnetic field (angle 10°) to induce molding.

[0111] Step 4: Pre-press 6MPa, anneal at 620℃ for 0.9h; sinter at 1040℃ with a heating rate of 3℃ / min and a vacuum of 10⁻³Pa for 2.4h to form the AlFe2 intermetallic compound plastic ordered phase.

[0112] Step 5: Aging at 830℃ for 2 hours, then applying a 2.5μm Zn-Ni coating.

[0113] Final performance: average grain size 1400nm (standard deviation 8%), Hc=1150kA / m, Br=1.23T, (BH) max=305kJ / m³, elongation=5.5%, raw material cost is 12% lower than Ti / Zr formulation, suitable for low-to-mid-range motor applications.

[0114] Example 8

[0115] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0116] Step 1: Select Nd 30.2%, Fe 67%, B 2%, rare earth functional unit Tb 1.3%, and plasticity control unit (Cu 0.3% + Ga 0.2%) by mass percentage; clean with 35kHz ultrasonic for 15 min, and vacuum dry at 95℃.

[0117] Step 2: Mechanical alloying powder preparation, with a rotation speed of 400 r / min and a ball-to-powder ratio of 16:1, to obtain alloy powder with an average particle size of 3000 nm and a particle size distribution standard deviation of 41 nm; mix with γ-glycidyl etheroxypropyltriethoxysilane (A-187) solution at a ratio of 1:0.04, and treat at 42℃ and 320 r / min for 40 min.

[0118] Step 3: Hold pressure at 13MPa and 24℃ for 7 minutes, then apply a 0.8T magnetic field (angle 6°) to induce molding.

[0119] Step 4: Pre-compression pressure 7MPa, annealing at 660℃ for 0.7h; heating to 1055℃ at 4℃ / min, vacuum degree 10⁻ 4 Sintering at Pa for 2 hours under these conditions forms a Cu-Ga composite enrichment zone plastic phase.

[0120] Step 5: Aging at 870℃ for 1.5h, then coating with a 4μm Zn-Ni / Al-Ti composite coating.

[0121] Final performance: average grain size 1800nm ​​(standard deviation 7%), Hc=1280kA / m, Br=1.26T, (BH)max=325kJ / m³, elongation up to 11%, and elongation maintained at 8.5% at low temperature (-40℃), suitable for flexible magnetic components in low temperature environment.

[0122] Example 9

[0123] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0124] Step 1: Select Nd 31.5%, Fe 66%, B 2.1%, rare earth functional elements (Dy 1.2% + Pr 0.8%), and plasticity regulating element Nb 0.4% by mass percentage; clean with 40kHz ultrasonic for 12 minutes and vacuum dry at 100℃.

[0125] Step 2: Air jet milling was performed at an inlet pressure of 0.75 MPa and a temperature of 28 °C to obtain an alloy powder with an average particle size of 1800 nm and a particle size distribution standard deviation of 39 nm. The powder was then mixed with an N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792) solution at a ratio of 1:0.035 and treated at 45 °C and 300 r / min for 35 min.

[0126] Step 3: Hold at 14MPa pressure and 22℃ for 6 minutes, then apply an 8kV / m electric field (angle 8°) to induce molding.

[0127] Step 4: Pre-compression pressure 8MPa, annealing at 710℃ for 0.6h; heating to 1065℃ at 3.8℃ / min, vacuum degree 10⁻ 4 Sintering at Pa for 1.8 h under these conditions resulted in the formation of NbB2 nanoparticle-reinforced grain boundaries.

[0128] Step 5: Aging at 890℃ for 1.2 hours, then coating with a 3μm Al-Ti coating.

[0129] Final performance: average grain size 1100nm (standard deviation 6%), Hc=1450kA / m, Br=1.29T, (BH)max=335kJ / m³, elongation=7.8%, magnetic performance decay rate of only 5% at 150℃ (12% decay rate of traditional formula), suitable for high temperature scenarios such as drive motors of new energy vehicles.

[0130] Example 10

[0131] This embodiment describes a method for preparing a plastically tunable NdFeB magnet with a homogeneous functional modular structure, comprising the following steps:

[0132] Step 1: Select Nd 28.5%, Fe 69.2%, B 1.5%, rare earth functional elements (La 1.2% + Ce 0.8%), and plasticity regulating element Ti 0.3% by mass percentage; clean with 28kHz ultrasonic for 22 minutes and vacuum dry at 88℃.

[0133] Step 2: Air jet milling was performed at an inlet pressure of 0.6 MPa and a temperature of 24 °C to obtain an alloy powder with an average particle size of 2200 nm and a particle size distribution standard deviation of 44 nm. The powder was then mixed with a vinyltriethoxysilane (A-151) solution at a ratio of 1:0.025 and treated at 38 °C and 280 r / min for 45 min.

[0134] Step 3: Hold at 11 MPa pressure and 19℃ for 9 minutes, then apply a 0.55T magnetic field (angle 12°) to induce molding.

[0135] Step 4: Pre-press 5.5MPa, anneal at 640℃ for 0.8h; sinter at 1030℃ with a heating rate of 3.2℃ / min and a vacuum of 10⁻³Pa for 2.2h to form a (Ce,La)-Ti composite oxide interface layer.

[0136] Step 5: Aging at 810℃ for 2.2h, then coating with a 2μm Zn-Ni coating.

[0137] Final performance: average grain size 1600nm (standard deviation 9%), Hc=1100kA / m, Br=1.21T, (BH) max=295kJ / m³, elongation=4.8%, heavy rare earth content reduced by 60%, raw material cost reduced by 25%, suitable for cost-sensitive home appliance motor scenarios.

[0138] The magnet of this invention, through homogeneous functional unit ordered structure design, significantly outperforms traditional NdFeB magnets that do not incorporate plasticity control functional units and do not employ ordered structure design in terms of magnetic properties (Hc, Br, (BH)max) and plasticity (elongation), demonstrating its technological advantages.

[0139] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A plastically tunable NdFeB magnet with a homogeneous functional unit sequence, comprising soft magnetic phase functional units, hard magnetic phase functional units, and plastic phase functional units, characterized in that: The neodymium iron boron magnet is composed of the following materials in mass percentage: 28-32% Nd, 66-70% Fe, 1-3% B, 0.1-5% rare earth functional units, and 0.1-1% plasticity control functional units; the rare earth functional units are one or more of Dy, Tb, and Pr; the plasticity control functional units are one or more of Al, Nb, Ti, Zr, Ce, La, Cu, or Ga; the soft magnetic phase functional units and the hard magnetic phase functional units form a three-dimensional ordered gradient structure system through exchange coupling; the plastic phase functional units are uniformly distributed at the grain boundaries of the soft magnetic phase functional units and the hard magnetic phase functional units, and form a gradient distribution with the distribution of the soft magnetic phase functional units and the hard magnetic phase functional units; the average size of the plastic phase functional units is 5-500 nm, and the thickness at the grain boundaries is 5-20 nm. The NdFeB magnet has an amorphous interface ordered layer of nm; the average grain size of the NdFeB magnet is 500~5000 nm, and the relative standard deviation (RSD) of the grain size is ≤10%; the coercivity of the NdFeB magnet at 20℃ is... H c ≥1000 kA / m, remanence B r ≥1.2 T, maximum magnetic energy product ( BH ) max ≥300 kJ / m 3 And the elongation rate is 1~12%.

2. The plastically tunable NdFeB magnet with a homogeneous functional unit sequence structure according to claim 1, characterized in that: The volume fraction of the soft magnetic phase functional unit is 1-30%, the volume fraction of the hard magnetic phase functional unit is 70-99%, and the volume fraction of the plastic phase functional unit is 0.1-5%, and the sum of the volume fractions of the three is 100%; the average particle size of the soft magnetic phase functional unit is 100-1000 nm and it is uniformly dispersed among the hard magnetic phase functional units, and the average grain size of the hard magnetic phase functional unit is 500-5000 nm.

3. A method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit order structure as described in any one of claims 1 or 2, characterized in that, Includes the following steps: Step 1, Raw material cleaning and impurity removal: Select raw materials according to mass percentage, including 28~32% Nd, 66~70% Fe, 1~3% B, 0.1~5% rare earth functional units and 0.1~1% plasticity regulation functional units, and then clean and remove impurities; Step 2, Powder Preparation and Modification: Using an air jet mill or mechanical alloying process, Nd, Fe, B, rare earth functional units, and plasticity control functional units are uniformly dispersed to obtain alloy powder with an average particle size of 300–3000 nm and a relative standard deviation (RSD) ≤ 10%. The alloy powder is then mixed and stirred with a silane coupling agent functional unit solution. Surface modification functional units further improve the dispersibility of the alloy powder, causing some Fe elements to form soft magnetic phase micronuclei α-Fe and Fe3B, while Nd, B, and some Fe elements form a hard magnetic phase precursor Nd2Fe. 14 B, Plasticity regulation functional units form plastic phase functional unit precursors through diffusion and reaction, completing the synergistic dispersion and particle size matching of the three phases to obtain modified powder; Step 3, External field induced pre-compression molding: The modified powder is loaded into the mold for pre-compression, and the pressure is maintained at 10~15MPa and 15~25℃ for 5~10min; the external field induced magnetic field strength is 0.5~1T, and the external field induced electric field strength is 1~10kV / m; and the angle between the direction of the magnetic field or electric field and the expected direction of plastic deformation is ≤15°. After the soft magnetic phase micronuclei are oriented and arranged, they drive the hard magnetic phase prototype to form an orderly distribution. The plastic phase functional unit precursor is dispersed in the grain boundary region and rheologically arranged synchronously with the arrangement of the soft magnetic phase micronuclei and the hard magnetic phase prototype, forming a homogeneous functional unit ordered structure molded blank. Step 4, Pre-press annealing and low-temperature sintering: The homogeneous functional unit ordered structure pre-treated the green body by pre-press annealing at 5~10 MPa, with an annealing temperature of 600~750℃ and an annealing time of 0.5~1h; through functional unit diffusion regulation, the rheologically arranged plasticity-regulated functional unit precursors form nano-tough plastic phase functional units in the grain boundary region; then, under a vacuum degree of 10 -3 ~10 -4 In a vacuum sintering furnace, the temperature is increased to 1020-1080℃ at a heating rate of 3-5℃ / min and held for 1.5-2.5h. This low-temperature sintering forms an amorphous interface layer of 5-20nm, allowing soft magnetic phase micronuclei to aggregate and grow in specific regions, while hard magnetic phase nascent grains grow, forming both soft and hard magnetic phase functional units, thus yielding Nd₂Fe₂. 14 B-type plasticity-regulated composite functional unit; Step 5, Aging heat treatment and coating: By applying Nd2Fe... 14 B. Plasticity-controlled composite functional units are heated to 800~950℃ for aging heat treatment, held for 1~10h and then cooled in the furnace to precipitate the controlled dislocation sequence structure, adjust the distribution of soft magnetic phase functional units, optimize the structure of hard magnetic phase functional units, and apply a 1~5 μm thick Zn-Ni or Al-Ti composite functional unit coating by physical vapor deposition. The Zn-Ni or Al-Ti composite functional unit coating enhances corrosion resistance and plastic deformation coordination, resulting in a plastically tunable NdFeB magnet with a homogeneous functional unit sequence structure.

4. The method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit sequence according to claim 3, characterized in that: The soft magnetic phase functional unit is one or more of α-Fe, Fe3B, Fe-Dy solid solution, and Fe-Tb solid solution; The hard magnetic phase functional unit is Nd2Fe 14 B, Pr2Fe 14 B、(Ce,Nd)2Fe 14 One or more of B; The functional units of the plastic phase are Al-rich regions, AlFe2 intermetallic compounds, TiB2 nanoparticles, TiC microparticles, ZrB2 nanoparticles, ZrC microparticles, CeFe2 Laves phase, and (Ce,Nd)2Fe. 14 B main phase, LaFe2 Laves phase, Nd-Cu composite phase, Cu enrichment region, Nd6Fe 13 Ga nanophase, Ga-RE micron composite phase, NbB2 nanoparticles, Nb-RE micron composite phase; TiB2+AlFe2 composite nanophase, TiC+Al enriched micron region, ZrB2 framework+Dy2Fe 14 B-shell, Nd6Fe 13 Ga nanophase + (Ce,Nd)2Fe 14 B main phase, Ga-Ce micron composite phase, NbB2 nanoparticles + Cu coated micron layer, TiB2 / ZrB2 eutectic nanophase, TiC / ZrC micron eutectic phase, AlFe2 nanoparticles + Nd6Fe 13 Ga micron phases or one or more.

5. The method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit sequence according to claim 3, characterized in that: The silane coupling agent functional unit solution is one of the following: γ-aminopropyltriethoxysilane solution, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane solution, γ-glycidyl etheroxypropyltrimethoxysilane solution, γ-glycidyl etheroxypropyltriethoxysilane solution, γ-methacryloyloxypropyltrimethoxysilane solution, vinyltriethoxysilane solution, γ-mercaptopropyltrimethoxysilane solution, or γ-mercaptopropyltriethoxysilane solution; The surface-modifying functional unit is one of the following: γ-aminopropyltriethoxysilane solution, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane solution, γ-glycidyl etheroxypropyltrimethoxysilane solution, γ-glycidyl etheroxypropyltriethoxysilane solution, γ-methacryloyloxypropyltrimethoxysilane solution, vinyltriethoxysilane solution, γ-mercaptopropyltrimethoxysilane solution or γ-mercaptopropyltriethoxysilane solution, isopropyltris(dioctylpyrophosphate)titanate, tetraisopropyldi(dioctylphosphite)titanate, distearate, stearic acid, or oleic acid.

6. The method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit sequence according to claim 4, characterized in that: The volume fraction of the soft magnetic phase functional unit is 1-30%; the volume fraction of the hard magnetic phase functional unit is 70-99%; the volume fraction of the plastic phase functional unit is 0.1-5%; and the sum of the volume fractions of the plastic phase functional unit, the soft magnetic phase functional unit, and the hard magnetic phase functional unit is 100%.

7. The method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit sequence according to claim 4, characterized in that: The average particle size of the soft magnetic phase functional unit is 100~1000nm, and it is uniformly dispersed among the hard magnetic phase functional units; the average grain size of the hard magnetic phase functional unit is 500~5000nm; the average size of the plastic phase functional unit is 5~500nm, and it forms a gradient distribution with the distribution of the soft magnetic phase and the hard magnetic phase.

8. The method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit sequence according to claim 4, characterized in that: The cleaning and impurity removal in step 1 specifically involves: ultrasonic cleaning at a frequency of 20-40 kHz for 10-30 minutes, followed by cleaning under a vacuum of 10... -2 Impurities are removed by vacuum drying at a temperature of 80~100℃. The specific steps of step 2, namely the air jet milling or mechanical alloying process, are as follows: the air jet mill inlet pressure is controlled at 0.6~0.8MPa and the temperature at 20~30℃, or the mechanical alloying speed is controlled at 200~500r / min and the ball-to-material ratio is controlled at 10~20:

1. The mixing and stirring process in step 2 specifically involves mixing the alloy powder with the silane coupling agent functional element solution at a mass ratio of 1:0.01~0.05, and then treating the mixture at 30~50℃ and a stirring rate of 200~400 r / min for 30~60 min.

9. The method for preparing a plastically tunable NdFeB magnet with a homogeneous functional unit sequence according to claim 4, characterized in that: The thickness of the amorphous interface ordered layer is controlled to be 5-20 nm by adjusting the content of the plasticity regulation functional unit (0.1-1%) and the annealing temperature (600-750℃).

10. The method for preparing a homogeneous functional modular ordered plastic tunable NdFeB magnet according to claim 4, characterized in that: In step 5, the Zn-Ni or Al-Ti composite functional element coating enhances the bond between the coating and the substrate through metallic bonds.

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